Salt Marshes Remove Carbon Dioxide and Slow Down Climate Change

Greenhouse gas carbon dioxide acts like an atmospheric blanket trapping Earth's heat and abundance of carbon dioxide can alter the global climate. And warming climate causes the polar ice to melt thereby causing the sea levels to rise.

However, a warming climate and rising sea levels enable salt marshes to rapidly capture and remove carbon dioxide from the atmosphere. There by playing a role in slowing the rate of climate change.

Salt marshes, are made up mostly of grasses, are important coastal ecosystems, helping to protect shorelines from storms and providing habitat for a diverse range of wildlife, from birds to mammals, shell and fin-fishes and mollusks. They also build up coastal elevations by trapping sediment during floods, and produce new soil from roots and decaying organic matter.

This study was led by University of Virginia environmental scientist and the details were processed in the Sept.27 issue of the journal Nature.

The endless human activities are responsible for the increase of carbon dioxide, such as burning of fossil fuels to energize a rapidly growing world human population.

"We predict that marshes will absorb some of that carbon dioxide, and if other coastal ecosystems -- such as sea grasses and mangroves -- respond similarly, there might be a little less warming," said the study's lead author, Matt Kirwan, a research assistant professor of environmental sciences in the College of Arts & Sciences.

"One of the cool things about salt marshes is that they are perhaps the best example of an ecosystem that actually depends on carbon accumulation to survive climate change: The accumulation of roots in the soil builds their elevation, keeping the plants above the water," Kirwan said.

Salt marshes store enormous quantities of carbon that are essential to plant productivity. Even as the grasses die, the carbon remains trapped in the sediment. The researchers' model predicts that under faster sea-level rise rates, salt marshes could bury up to four times as much carbon as they do now.

"Our work indicates that the value of these ecosystems in capturing atmospheric carbon might become much more important in the future, as the climate warms," Kirwan said.

But the study also shows that marshes can survive only moderate rates of sea level rise. If seas rise too quickly, the marshes could not increase their elevations at a rate rapid enough to stay above the rising water. And if marshes were to be overcome by fast-rising seas, they no longer could provide the carbon storage capacity that otherwise would help slow climate warming and the resulting rising water.

"At fast levels of sea level rise, no realistic amount of carbon accumulation will help them survive," Kirwan noted.